Over the years, many different catalysts have been developed for producing bisphenol A (BPA). For example, US 2002/0147241 discloses an ion exchange bed for producing bisphenol A from phenol and acetone in a fixed bed reactor containing a gel-form or macroporous sulfonic acid ion exchange resin catalyst bed that has an upper layer and a lower layer and EP1222960A3 discloses a catalyst for producing bisphenol A that comprises strongly acidic cation-exchange resin spheres produced from a polystyrene/divinylbenzene (PS/DVB) copolymer sulfonated under conditions to introduce sulfone cross-linking.
In general, commercial processes for producing bisphenols, for example, BPA, typically use sulfonated, cross-linked polystyrene ion exchange resins (IER) with a mercapto co-promoter. These ion exchange resins are either 2 or 4% cross-linked polystyrene with divinylbenzene as the cross-linking agent and are either mono- or polydispersed materials with a typical particle size of 300 to 1,200 micrometers. The particles are gel-like in nature, which means that the reactants need to diffuse to a great extent into the particle to get to the active sulfonic acid sites and the resultant products then need to diffuse out. Due to the slow diffusion in the gel-like matrix of the ion exchange resin particles, the resulting commercial reactors are big vessels, have long residence times for the reaction, and can result in a wide variety of by-products, for example, tri-phenols and tetra-phenols.
In addition to the diffusion issues that arise when using gel-like ion exchange resins, these resins suffer from compressibility issues that arise due to the fluid flow during the reaction. The compressibility issues of the gel-like ion exchange resin limits the flow rate of the feed when used in a down flow reactor, requiring reactors with larger diameters to be used. The compressibility issues of gel-like ion exchange resins limits the flow rate of the feed when used in an up flow reactor due to the fluidization of the catalyst bed.
An improved catalyst for the production of bisphenols, for example, bisphenol A is desirable.